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Inventory & Monitoring Research & Projects: January, 2009

The moths that make up birds’ meals: DNA “bar-codes” used to identify prey of the Whip-poor-will.

Usually, scientists use traditional taxonomy—a system based on physical characteristics, such as the number of wing spots or legs—to identify species. Increasingly, however, scientists are looking within the cells of plants and animals to identify them, with the help of molecular geneticists interested in biodiversity. Together they are bringing new insights to taxonomy, genetics, ecology and park stewardship.

Over the last several years, scientists have taken mitochondrial DNA (mtDNA) samples from about 1,000 (out of 1,600 known) species of moths in the park. This mtDNA is inherited from moth’s mothers, and functions within the cell to turn food into energy the moth can use. With mtDNA we cannot tell individuals apart but it is useful for identifying which creatures are related; we couldn’t tell Bob and Sally apart using their mtDNA, for example, but we could tell that they are human and maybe even related. Researchers working with the moths can rapidly “read” a segment of the mtDNA and compare that record with a library of these samples. By doing this, they can identify the moth species from just a small amount of otherwise unidentifiable tissue such as eggs, larvae or even digested stomach contents from birds.

In this case, the bird whose meal is in question is the Whip-poor-will (Caprimulgus vociferus). These are medium sized nocturnal birds that feed on insects while flying. Little is known about certain aspects of their life history, including what their prey species are. We would like to know, because they are thought to be declining in some regions of the eastern United States.

When a whip-poor-will was killed by a vehicle in the Park in 2008, the stomach contents were removed and sent to the University of Guelph’s Biodiversity Institute of Ontario. Researcher Elizabeth Clare was able to extract mtDNA sequences of four different species of moths from the “soupy” gut contents of the birds. Upon analysis, she found that one of the moths in that meal was rather uncommon.

This is thought to be the first instance of moth species being identified from bird gut contents, and it opens up the potential for new ecological investigations. Researchers with the All Taxa Biodiversity Inventory (ATBI), a project to identify all species in the park, have also sequenced the mtDNA of many aquatic insects in the Smokies, and the cataloguing of some groups such as birds is completed nationally.

Abrams Creek flows through a huge watershed: at 48,854 acres, it’s one of the largest in Great Smoky Mountains National Park. It’s also one of the most threatened: silt (very fine soil particles) and pollutants from development outside the park may change this creek, which is home to three fish and one plant species that are extremely rare in the United States, and a number of species often found only in Tennessee. To better manage the threat of pollution, park botanists and entomologists need to document current conditions (what they call a “baseline”), which includes what plants and animals live in the water now, and where they are located in the stream. Over the years, with funding from the Tallassee Fund, they will monitor changes in the plants’ and animals’ health, numbers, and locations to see how potential development may impact them.

To document baseline conditions, scientists collected insects, small water invertebrates such as snails, and plants at several sites in Abrams Creek during summer, 2008. While scientists have not analyzed all of the baseline data yet, they noticed that the diversity of plants and animals seemed to be lower in one tributary coming into Abrams Creek than in other streams they’ve studied in the National Park. They also noticed a large amount of algae in one section of stream—often a sign of high levels of pollutants such as fertilizer, sewage, or farm runoff, or highly acidic waters—and sent samples to the University of Tennessee to try to find out why.

Scientists also took a close look at a Tennessee endangered aquatic plant, large-leaf pondweed (Potamogeton amplifolius). While its name may not be exciting, finding one in the park is. In fact, this is the only known location of the large-leaf pondweed in the National Park. The Park’s botanist and her technician slogged through Abrams Creek and finally found a group of these plants in a narrow gorge, where they carefully took GPS (Geographical Positioning System) points to make sure they could find and monitor them in the future. They also found colonies of a federally threatened shrub, Virginia spiraea (Spiraea virginiana) that botanists had marked in the 1990s. The shrubs, which reproduce by making clones of themselves, seemed to be doing well. National Park Service and U.S. Fish and Wildlife Service scientists will collaborate to monitor numbers and locations of this rare shrub in the future.